The aim of this study was to investigate the role of apelin in the cell proliferation and autophagy of lung adenocarcinoma. The over-expression of APJ in lung adenocarcinoma was detected by immunohistochemistry, while plasma apelin level in lung cancer patients was measured by enzyme-linked immunosorbent assay. Our findings revealed that apelin-13 significantly increased the phosphorylation of ERK1/2, the expression of cyclin D1, microtubule-associated protein 1 light chain 3A/B (LC3A/B), and beclin1, and confirmed that apelin-13 promoted A549 cell proliferation and induced A549 cell autophagy...